package set;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class Demo {
	
	public static void main(String[] args) {
		Set<String> set = new HashSet<>();
		String s1 = "wanglong";
		String s2 = "wanglong";
		set.add(s1);
		
		Map<String, Integer> map = new HashMap<>();
		System.out.println(map.get("i"));
		
		System.out.println(set.add(s2));
		
		System.err.println(set.remove("ok"));
	}

}
